Vehicle speed control apparatus and method

ABSTRACT

The present disclosure describes systems and methods for controlling the speed of a vehicle comprising: during a pulse phase of cruise control, applying engine torque to raise speed, the amount and duration of which being responsive to engine speed; and during a glide phase of cruise control, discontinuing engine combustion. In this way cruise control may maintain a mean speed equivalent to a desired, threshold speed while reducing fuel consumption, and NVH effects felt by the end user compared to traditional cruise control methods.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application claims priority to United Kingdom PatentApplication Number 1203312.2, filed on Feb. 27, 2012, the entirecontents of which are hereby incorporated by reference for all purposes.

TECHNICAL FIELD

The present application relates to a vehicle speed control apparatus andmethod.

BACKGROUND AND SUMMARY

The present disclosure relates to controlling the speed of a vehicleduring a cruise control mode to increase fuel economy and/or emissions.

Cruise control systems are provided within vehicles to automaticallycontrol the vehicle's speed without any input, such as operation of theaccelerator pedal, by the driver. Typically, a set point value relatedto the desired speed is defined by the driver. The vehicle speed isautomatically controlled until the driver intervenes, such as byoperating one or more of the brake, clutch, accelerator or mode switch.

Known adaptive cruise control systems can also provide automatic brakingor dynamic set speed type controls. Automatic braking systems allow avehicle to keep pace with the car it is following, slow when closing inon the vehicle in front and accelerate again to the threshold speed whentraffic allows. Dynamic set speed uses the GPS position of speed limitsigns to set the threshold speed.

Existing speed control algorithms can accurately maintain vehicle speedat the threshold speed, even under varying road gradients. However,these algorithms are not optimized for fuel economy or emissions. It isknown that, even when traversing varying road gradients with gentleslopes, this can be done more economically by a skilled driver. Thedriver can maintain a relatively constant throttle position and allowthe vehicle to accelerate on the downgrades and decelerate on upgrades,the driver reducing power when cresting a rise and increasing powerbefore an upgrade is reached. Known cruise control systems tend toover-throttle on the upgrades and retard on the downgrades, thus wastingthe energy available from the inertia of the vehicle.

Internal combustion engines operate most efficiently in terms of brakespecific fuel consumption (BSFC) at a particular combination of enginespeed, and torque. However, when cruising at constant speed the enginemay be far from the optimal BSFC operating point.

Most speedometers have a tolerance of around±10%. Vehicle manufacturerstypically calibrate speedometers to read high by an amount equal to theaverage error to ensure that the speedometer does not indicate a lowerspeed than the actual speed of the vehicle.

Systems and methods for controlling the speed of a vehicle are providedcomprising: during a pulse phase of cruise control, applying enginetorque to raise speed, the amount and duration of which being responsiveto engine speed; and during a glide phase of cruise control,discontinuing engine combustion. In this way cruise control may maintaina mean speed equivalent to a desired, threshold speed while reducingfuel consumption, and NVH effects compared to traditional cruise controlmethods.

The above advantages and other advantages, and features of the presentdescription will be readily apparent from the following DetailedDescription when taken alone or in connection with the accompanyingdrawings.

It should be understood that the summary above is provided to introducein simplified form a selection of concepts that are further described inthe detailed description. It is not meant to identify key or essentialfeatures of the claimed subject matter, the scope of which is defineduniquely by the claims that follow the detailed description.Furthermore, the claimed subject matter is not limited toimplementations that solve any disadvantages noted above or in any partof this disclosure. Further, the inventors herein have recognized thedisadvantages noted herein, and do not admit them as known.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an example cylinder of an internal combustion engine.

FIG. 2 is a flow chart of a cruise control method according to thedisclosure.

FIG. 3 is a flow chart of methods for controlling NVH due to enacting acruise control method in accordance with the present disclosure.

FIG. 4 shows a map of the brake specific fuel consumption for givenengine torque and speed.

FIG. 5 shows example embodiments of vehicle speed during pulse and glidephases in accordance with the present disclosure.

DETAILED DESCRIPTION

Referring now to the figures, FIG. 1 depicts an example embodiment of acombustion chamber or cylinder of internal combustion engine 10. Engine10 may receive control parameters from a control system includingcontroller 12 and input from a vehicle operator 130 via an input device132. In this example, input device 132 includes an accelerator pedal anda pedal position sensor 134 for generating a proportional pedal positionsignal PP. Also included is an input switch 133 for generating a cruisecontrol signal CC. Cylinder (herein also “combustion chamber’) 14 ofengine 10 may include combustion chamber walls 136 with piston 138positioned therein. Piston 138 may be coupled to crankshaft 140 so thatreciprocating motion of the piston is translated into rotational motionof the crankshaft. Crankshaft 140 may be coupled to at least one drivewheel of the passenger vehicle via a transmission system. Further, astarter motor may be coupled to crankshaft 140 via a flywheel to enablea starting operation of engine 10.

Cylinder 14 can receive intake air via a series of intake air passages142, 144, and 146. Intake air passage 146 may communicate with othercylinders of engine 10 in addition to cylinder 14. In some embodiments,one or more of the intake passages may include a boosting device such asa turbocharger or a supercharger. For example, FIG. 1 shows engine 10configured with a turbocharger including a compressor 174 arrangedbetween intake passages 142 and 144, and an exhaust turbine 176 arrangedalong exhaust passage 148. Compressor 174 may be at least partiallypowered by exhaust turbine 176 via a shaft 180 where the boosting deviceis configured as a turbocharger. However, in other examples, such aswhere engine 10 is provided with a supercharger, exhaust turbine 176 maybe optionally omitted, where compressor 174 may be powered by mechanicalinput from a motor or the engine. A throttle 20 including a throttleplate 164 may be provided along an intake passage of the engine forvarying the flow rate and/or pressure of intake air provided to theengine cylinders. For example, throttle 20 may be disposed downstream ofcompressor 174 as shown in FIG. 1, or alternatively may be providedupstream of compressor 174.

Exhaust passage 148 may receive exhaust gases from other cylinders ofengine 10 in addition to cylinder 14. Exhaust gas sensor 128 is showncoupled to exhaust passage 148 upstream of emission control device 178.Sensor 128 may be selected from among various suitable sensors forproviding an indication of exhaust gas air/fuel ratio such as a linearoxygen sensor or UEGO (universal or wide-range exhaust gas oxygen), atwo-state oxygen sensor or EGO (as depicted), a HEGO (heated EGO), aNOx, HC, or CO sensor, for example. Emission control device 178 may be athree way catalyst (TWC), NOx trap, various other emission controldevices, or combinations thereof.

Exhaust temperature may be measured by one or more temperature sensors(not shown) located in exhaust passage 148. Alternatively, exhausttemperature may be inferred based on engine operating conditions such asspeed, load, air-fuel ratio (AFR), spark retard, etc. Further, exhausttemperature may be computed by one or more exhaust gas sensors 128. Itmay be appreciated that the exhaust gas temperature may alternatively beestimated by any combination of temperature estimation methods listedherein.

Each cylinder of engine 10 may include one or more intake valves and oneor more exhaust valves. For example, cylinder 14 is shown including atleast one intake poppet valve 150 and at least one exhaust poppet valve156 located at an upper region of cylinder 14. In some embodiments, eachcylinder of engine 10, including cylinder 14, may include at least twointake poppet valves and at least two exhaust poppet valves located atan upper region of the cylinder.

Intake valve 150 may be controlled by controller 12 by cam actuation viacam actuation system 151. Similarly, exhaust valve 156 may be controlledby controller 12 via cam actuation system 153. Cam actuation systems 151and 153 may each include one or more cams and may utilize one or more ofcam profile switching (CPS), variable cam timing (VCT), variable valvetiming (VVT) and/or variable valve lift (VVL) systems that may beoperated by controller 12 to vary valve operation. The operation ofintake valve 150 and exhaust valve 156 may be determined by valveposition sensors (not shown) and/or camshaft position sensors 155 and157, respectively. In alternative embodiments, the intake and/or exhaustvalve may be controlled by electric valve actuation. For example,cylinder 14 may alternatively include an intake valve controlled viaelectric valve actuation and an exhaust valve controlled via camactuation including CPS and/or VCT systems. In still other embodiments,the intake and exhaust valves may be controlled by a common valveactuator or actuation system, or a variable valve timing actuator oractuation system. A cam timing may be adjusted (by advancing orretarding the VCT system) to adjust an engine dilution in coordinationwith an EGR flow thereby reducing EGR transients and improving engineperformance.

Cylinder 14 can have a compression ratio, which is the ratio of volumeswhen piston 138 is at bottom center to top center. Conventionally, thecompression ratio is in the range of 9:1 to 10:1. However, in someexamples where different fuels are used, the compression ratio may beincreased. This may happen, for example, when higher octane fuels orfuels with higher latent enthalpy of vaporization are used. Thecompression ratio may also be increased if direct injection is used dueto its effect on engine knock.

In some embodiments, each cylinder of engine 10 may include a spark plug192 for initiating combustion. Ignition system 190 can provide anignition spark to combustion chamber 14 via spark plug 192 in responseto spark advance signal SA from controller 12, under select operatingmodes. However, in some embodiments, spark plug 192 may be omitted, suchas where engine 10 may initiate combustion by auto-ignition or byinjection of fuel as may be the case with some diesel engines.

As a non-limiting example, cylinder 14 is shown including one fuelinjector 166. Fuel injector 166 is shown coupled directly to cylinder 14for injecting fuel directly therein in proportion to the pulse width ofsignal FPW received from controller 12 via electronic driver 168. Inthis manner, fuel injector 166 provides what is known as directinjection (hereafter also referred to as “DI”) of fuel into combustioncylinder 14. While FIG. 1 shows injector 166 as a side injector, it mayalso be located overhead of the piston, such as near the position ofspark plug 192. Fuel may be delivered to fuel injector 166 from a highpressure fuel system 8 including fuel tanks, fuel pumps, and a fuelrail. Alternatively, fuel may be delivered by a single stage fuel pumpat lower pressure, in which case the timing of the direct fuel injectionmay be more limited during the compression stroke than if a highpressure fuel system is used. Further, while not shown, the fuel tanksmay have a pressure transducer providing a signal to controller 12. Itwill be appreciated that, in an alternate embodiment, injector 166 maybe a port injector providing fuel into the intake port upstream ofcylinder 14.

As described above, FIG. 1 shows one cylinder of a multi-cylinderengine. As such each cylinder may similarly include its own set ofintake/exhaust valves, fuel injector(s), spark plug, etc.

While not shown, it will be appreciated that engine may further includeone or more exhaust gas recirculation passages for diverting at least aportion of exhaust gas from the engine exhaust to the engine intake. Assuch, by recirculating some exhaust gas, an engine dilution may beaffected which may reduce engine knock, peak cylinder combustiontemperatures and pressures, throttling losses, and NOx emissions. Theone or more EGR passages may include an LP-EGR passage coupled betweenthe engine intake upstream of the turbocharger compressor and the engineexhaust downstream of the turbine, and configured to provide lowpressure (LP) EGR. The one or more EGR passages may further include anHP-EGR passage coupled between the engine intake downstream of thecompressor and the engine exhaust upstream of the turbine, andconfigured to provide high pressure (HP) EGR. In one example, an HP-EGRflow may be provided under conditions such as the absence of boostprovided by the turbocharger, while an LP-EGR flow may be providedduring conditions such as in the presence of turbocharger boost and/orwhen an exhaust gas temperature is above a threshold. The LP-EGR flowthrough the LP-EGR passage may be adjusted via an LP-EGR valve while theHP-EGR flow through the HP-EGR passage may be adjusted via an HP-EGRvalve (not shown).

Controller 12 is shown in FIG. 1 as a microcomputer, includingmicroprocessor unit 106, input/output ports 108, an electronic storagemedium for executable programs and calibration values shown as read onlymemory chip 110 in this particular example, random access memory 112,keep alive memory 114, and a data bus. Controller 12 may receive varioussignals from sensors coupled to engine 10, in addition to those signalspreviously discussed, including measurement of inducted mass air flow(MAF) from mass air flow sensor 122; engine coolant temperature (ECT)from temperature sensor 116 coupled to cooling sleeve 118; a profileignition pickup signal (PIP) from Hall effect sensor 120 (or other type)coupled to crankshaft 140; throttle position (TP) from a throttleposition sensor; and manifold absolute pressure signal (MAP) from sensor124. Engine speed signal, RPM, may be generated by controller 12 fromsignal PIP. Engine speed may be displayed on tachometer 135. Manifoldpressure signal MAP from a manifold pressure sensor may be used toprovide an indication of vacuum, or pressure, in the intake manifold.Still other sensors may include fuel level sensors and fuel compositionsensors coupled to the fuel tank(s) of the fuel system.

Storage medium read-only memory 110 can be programmed with computerreadable data representing instructions executable by processor 106 forperforming the methods described below as well as other variants thatare anticipated but not specifically listed. Furthermore an enginecontroller may be adapted to determine a brake specific fuel consumptionvalue for a given engine speed and torque and maximize fuel efficiencybased on these values. At least one of the first and the secondpredetermined values may be dependent on the brake specific fuelconsumption value for the respective vehicle speed. This information maybe predetermined and stored in in an engine control unit, for example.

FIG. 2 shows a method of automatically controlling the speed of avehicle. The method is carried out by an automatic speed controlapparatus. This apparatus may be part of the engine controller of thevehicle or a separate component communicatively connected to thecontroller. The apparatus may comprise a controller 12 comprising aprocessor 106 and memory, such as read only memory 110, and varioussensors for measuring engine parameters and vehicle speed.

The apparatus may be operatively coupled to the fuel supply system ofthe vehicle. The apparatus may be adapted to at least one of increase ordecrease the amount of fuel supplied to the engine to cause vehicleacceleration.

The apparatus may be operatively coupled to the vehicle transmission.The apparatus may be adapted to decouple the vehicle wheels from theengine. The apparatus may be adapted to disengage a transmission clutchof the vehicle.

The apparatus also includes an input switch, which is operable by thedriver and causes the apparatus to enter a cruise control mode. At step202, the processor continuously monitors the state of the switch. If notoperated (NO) the processor returns to monitoring the switch. If inputis received indicated the cruise control switch has been operated (YES),the apparatus enters the cruise control mode and moves to step 204.

At 204, the processor determines a threshold speed. This initiallycorresponds to the current speed of the vehicle and so the processorsets the threshold speed to the sensed current speed. However, theprocessor may be adapted such that the threshold speed is adjustable bythe driver during cruise control.

Next, at step 206, various engine parameters are sensed. Theseparameters may be engine speed, load, AFR and others. At step 208, afirst predetermined value is determined. This value is dependent on theengine parameters and is selected to provide an optimal brake specificfuel consumption (BSFC) performance from the engine. However, an upperthreshold may also be applied, such as that the first predeterminedvalue is not greater than 10% of the threshold speed. A first value maybe determined based on engine speed and torque output and may vary withbrake specific fuel consumption for a given output. This will bedescribed in greater detail below with reference to FIG. 4.

At step 210, the processor sends a signal to increase the amount of fueldelivered to the engine. This causes an increase in the vehicle speed.

At step 212, the current vehicle speed is sensed. The processor includesa comparator unit and, at step 214, the current vehicle speed iscompared to a sum of the threshold speed and the first predeterminedvalue. If the current vehicle speed is less than this sum (NO at 214)then the method returns to step 210 to further increase the supply offuel. If the current vehicle speed has reached or exceeded the sum (YESat 214) then the method continues to step 216.

At step 216, the various engine parameters are again sensed. At step218, a second predetermined value is determined. This value is alsoselected to provide an optimal BSFC performance from the engine. Theoptimal BSFC value will have changed as it is dependent on engine speedwhich will have changed as vehicle speed has been increased. A lowerthreshold may not be applied to avoid speed violations but may beapplied to minimize the magnitude of the fluctuating around thethreshold speed.

The first predetermined value or proportion may be substantially equalto the second predetermined value or proportion.

At least one of the first and the second predetermined values may bedependent on at least one engine parameter. At least one of the firstand the second predetermined values may be dependent on the brakespecific fuel consumption value for the respective vehicle speed. Atleast one of the first and the second predetermined values may beselected to produce an optimal brake specific fuel consumption valuefrom the engine.

At least one of the first and second predetermined proportions may be apredetermined proportion or percentage above the threshold speed. Thepredetermined percentage may be 10% or less.

The method may include providing a controller comprising a processor andmemory for carrying out the method. The predetermined values orproportions may comprise values or proportions stored in memory.

Alternatively, the predetermined values or proportions may be determinedfrom a stored algorithm. The predetermined values or proportions may bedetermined in real time. The predetermined values or proportions may bedetermined just prior to changing the vehicle speed.

The predetermined values or proportions may comprise values orproportions stored in the memory.

At step 220, the processor sends a signal to decrease the amount of fueldelivered to the engine. This causes a decrease in the vehicle speed. Inanother embodiment, engine combustion may be discontinued during this“glide” phase of cruise control.

At step 222, the current vehicle speed is again sensed. At 224, theprocessor then compares the current vehicle speed with a difference ofthe threshold speed and the second predetermined value. If the currentvehicle speed is greater than this difference (NO at 224), then themethod returns to step 220 to further decrease the supply of fuel.

If the current vehicle speed has decreased such that it is equal or lessthan the calculated difference (YES at 224) then the method returns.Therefore, the method repeats the steps of increasing and decreasing thevehicle speed as long as the cruise control switch is operated. Thecruise control switch may be turned off by a user input thus exiting thecruise control mode. However, in another, non-limiting example thecruise control switch may be turned off by another input, such as from acollision avoidance system.

Utilizing the method of the present disclosure small variations invehicle speed around the threshold speed are allowed to occur in orderto alternately operate close to the BSFC for short durations where thefueling is increased. These pulse periods are followed by periods ofglide, under no load the vehicle is allowed to coast. During thesecoasting periods, fueling will either be removed altogether, with thevehicle driving the engine, or maintained at a level sufficient tobalance engine drag torque, but providing no torque to the wheels. Inthis way the vehicle speed will maintain a mean value around thethreshold speed, but the fuel consumption will be reduced versus aconstant fueling regime.

In an alternative embodiment, the step of decreasing the vehicle speedmay involve decoupling the vehicle wheels from the engine, such as bydisengaging a transmission clutch of the vehicle.

The present disclosure allows small variations in vehicle speed aroundthe threshold speed in order to operate at or close to the optimal BSFC.Using the pulse and glide approach, the vehicle speed will have a meanvalue around the threshold speed, but the fuel consumption will bereduced in comparison to a constant fueling regime.

A cruise control apparatus of the present disclosure may further be anadaptive automatic speed control apparatus. The apparatus may include adetecting system, such as radar, to detect a vehicle in front anddetermining a distance to the vehicle in front. The apparatus may beadapted to maintain the vehicle within a distance range to the vehiclein front.

The disclosure may comprise an adaptive speed control method andapparatus which utilizes a forward looking radar system to detect thedistance to the vehicle in front. This distance may be dynamicallymanaged to allow the increasing and decreasing speed of the vehicle.

The threshold speed may at least initially correspond to the currentspeed of the vehicle. The threshold speed may be adjustable by thedriver during the cruise control mode.

The step of increasing the vehicle speed may comprise increasing theamount of fuel supplied to the engine to cause vehicle acceleration.

The step of decreasing the vehicle speed may comprise decreasing theamount of fuel supplied to the engine to cause vehicle deceleration.Alternatively, the step of decreasing the vehicle speed may comprisedecoupling the vehicle wheels from the engine. The step of decreasingthe vehicle speed may comprise disengaging a transmission clutch of thevehicle.

Alternatively or in addition, at least one of the steps of increasingand decreasing the vehicle speed may comprise passively allowing thevehicle speed to increase or decrease respectively due to roadgradients, cutting engine power or the like. Therefore, the terms“increasing” and “decreasing” are intended to include taking an actionwhich indirectly causes, or passively allows, the change in speed.

The method may include adaptively controlling the speed of the vehicle.The method may include detecting a vehicle in front and determining adistance to the vehicle in front. The method may include maintaining thevehicle within a distance range to the vehicle in front. The step of atleast one of increasing the vehicle speed, decreasing the vehicle speed,calculating the first predetermined value and calculating the secondpredetermined value may be dependent on the distance to the vehicle infront.

The above method may affect characteristics of the vehicle and/orengine, such as noise, vibration, and harshness (NVH) characteristics.FIG. 3 shows a flowchart of methods that may be enacted to minimizeaudio, visual or tactile phenomena manifested as NVH characteristicsassociated with or produced by the cruise control mode. The method 300starts with an engine on event than proceeds to step 302 where it isdetermined if the cruise control switch has been operated. If at 302,the cruise control switch has not been operated (NO) the method ends.

If, at 304, the cruise control switch has been operated (YES) the methodproceeds to 304 where actions are taken to minimize NVH characteristicsthat may be caused by enacting a cruise control method in accordancewith the present disclosure. The actions listed in step 304 occurconcomitantly with steps, which may be those outlined in FIG. 2, tocontrol vehicle speed. At 306, the duty cycle may be varied to minimizelarge gains and losses in vehicle speed. Varying the duty cycle mayinvolve varying the torque applied to reach a speed a first value abovea threshold speed, described in greater detail below in reference toFIG. 5. Varying the duty cycle may also involve reducing the magnitudeof fluctuation in speed as described below and further in reference toFIG. 5

At 308, the magnitude of fluctuation around threshold speed may beminimized. In one example, this may mean the first and second values arereduced such that they are less different from the threshold speed andthus changes in speed are reduced due to the narrow range of speedsvisited by the cruise control device. This is described in furtherdetail below in reference to FIG. 5

At 310, the aggressiveness of the change in speed is minimized. This maymean that transitions in fueling and throttle actuations anddeactivations are made to be more gradual. This may be accomplished by areadable program stored and carried out by engine controller 12. Exampleembodiments with varied aggressive in speed change are shown anddescribed below in reference to FIG. 5

At 312, another example of reducing NVH may be filtering tachometeroutput to alter the display. Some methods of increasing and decreasingvehicle speed involve rapid and/or large changes in engine speed andthis may be noticeable to the driver from the tachometer display. Thismay be mitigated using a tachometer filtering algorithm. The method 300then returns.

Several of the actions shown at step 304 may be undertakensimultaneously or, in another example, one may be enacted at a time.Enacting the various methods to minimize negative NVH characteristicsdue to cruise control may be further responsive to additional input fromsensors. For example, large changes in engine speed as indicated by ahall effect sensor may trigger a filtering algorithm for the tachometerdisplay. Such large changes may further trigger a minimization ofmagnitude of fluctuations around the threshold speed. After steps tominimize NVH characteristics have been enacted they may be continued aslong as the cruise control switch is operated. In an alternate example,these methods may occur when triggered by particular sensors or underparticular cruise control conditions.

Referring now to FIG. 4, a map is shown of brake specific fuelconsumption for given engine speeds and torques. High efficiency range402 shows a region of torques and speeds at which a given engineoperates at optimal fuel economy. Mid efficiency range 404 shows wherean engine may operate moderately efficiently and low efficiency range506 shows the region of torque and engine speeds at which the engine mayoperate less efficiently to provide a given output. Brake specific fuelconsumption maps such as that shown in FIG. 4 may be stored in read onlymemory 110 of engine controller 12 and used in conjunction with engineoperating parameters in determining a first and second value around agiven threshold vehicle speed.

For example if a cruise control switch is operated at a given enginespeed and torque there may be a range of values to maintain theapproximate resultant vehicle speed. A first value may be chosen basedin that range to provide the maximal fuel efficiency for a given range.Examples of such ranges are shown at 407, 408, and 410. In the rangeindicated by 407, a first value may be chosen by controller 12 so thatvehicle speed is maintained by pulse phases with higher torque 412 suchthat during pulse phases of cruise control when fueling is increasedhigher torque values correspond to the most fuel efficient operation ofthe engine. Conversely, in the range indicated by 408, a lower torque414 may correspond to the maximal fuel efficiency which will be used tocalculate a first value once a cruise control switch has been operated.

In another example, a range 410 may exist where a middle torque valuemay provide the highest fuel economy in a given range. Brake specificfuel consumption maps such as the example shown may be used by an enginecontroller in declaring a first and second threshold value, but also indetermining how a target speed is reached, a concept described ingreater detail below in reference to FIG. 5.

A pulse phase in which fueling is increased in order to reach a vehiclespeed which is a first value above the threshold speed may vary in itslength (altering the duty cycle). For a given difference between thethreshold speed and a high speed, a longer duration of fueling (with ashallower slope) may correspond to a lesser rate of acceleration.Conversely, a steeper slope and shorter duration of fueling maycorrespond to a higher rate of acceleration. These durations may beadjusted to achieve maximal fuel economy and to minimize noise,vibration and harshness effects felt by a vehicle user. In addition tovariations in duty cycle and duration of fueling, fueling increases maynot be consistent for an entire pulse phase and an engine may be moreefficient in ramping up a fueling increase toward the end of a pulsephase, for example.

In one example, an engine torque applied during the pulse phase may beselected based on the current engine speed and the BSFC maps stored inthe controller. The controller may determine a range of availableapplied torque that will meet cruise control requirements (e.g., maximumduration of the pulse phase, minimum and maximum acceleration rates,etc.). Then, from the available range, the torque that minimizes fuelconsumption may be selected. This approach may be repeated for eachpulse phase given the engine speed for that phase. This may result in afirst torque value applied at a first engine speed in a first pulsephase in a first gear, and a second torque value applied at a secondengine speed in a second pulse phase in a second gear, such as due to agear shift between the first and second pulse phases. Because of thepotentially different speeds and the different positions in the BSFCmap, different torques limits may be selected to minimize the fuelconsumption (e.g., the first torque may be a torque at a higher end ofthe available range at the first speed, and the second torque may be atorque at a lower end of the available range at the second speed, suchas illustrated in FIG. 4). Accordingly, the amount of engine torqueapplied in the pulse phase may vary from one pulse event to anotherpulse event.

Referring now to FIG. 5 examples of vehicle speed variations under pulseand glide cruise control methods in accordance with the presentdisclosure are shown. In a first example 501 a vehicle speed isindicated by the solid black line. At 506 a user operates the cruisecontrol switch indicating a threshold speed 502. For given engineparameters and the selected vehicle threshold speed 502 enginecontroller 12 may calculate a first threshold and a second threshold.During a pulse phase 508 of cruise control, fueling is increased toreach a high speed comprising the threshold speed plus the first valueat 500. In the first example 501 the pulse phase 508 may increase insteepness (corresponding to faster acceleration) toward the end of apulse phase. The shape and slope of the pulse phase 508 may bedetermined by an engine controller based on operating parameters and ona brake specific fuel consumption map such as the example shown in FIG.4. The glide phase 510 is dependent on road conditions and drag on anengine. However, in some embodiments, the engine may be engaged tocounteract engine drag, but not apply torque to the wheels to propel thevehicle. In another example, during a glide phase of cruise controlengine combustion may be discontinued. The glide phase 510 may besubstantially the same regardless of a shape and slope of a pulse phase.

A second example 511 is shown with a smaller first and second value,such that difference between the high speed 512 (a first value in excessof the threshold speed 514) and the low speed 516 (a second value belowthe threshold speed 514) is less than the difference as shown in thefirst example 501. This difference between high and low speed may beadjusted to minimize NVH affects due to cruise control. Also in thesecond example, the pulse phase 520, after a cruise control switch hasbeen operated at 518, has a linear shape such that accelerationthroughout the pulse phase 520 is consistent.

In a third example 523, the pulse phase 532 is linear. However, in thethird example 523, the slope of the pulse phase 532 is shallower thanthat of the pulse phase 520 in the second example 511. A shallower slopecorresponds to a lesser rate of acceleration. Differences in slope ofthe pulse phase 532 and in a difference between threshold speed 502 anda high speed 500 and low speed 504 may vary a duty cycle and thus theduration of fueling, compared to another example. These variations induty cycle may be exploited to reduce noise, vibration, and harshnesscharacteristics due to pulse and glide type of cruise control.

In a fourth example 535, a pulse phase 544 may start with an aggressivefuel increase (steep starting slope) and transition into a more moderatefuel increase (applied torque). These types of variations in shape ofthe pulse phase may be exploited to vary the aggressiveness of fuelingincrease (torque application, higher or lower) in different regions of apulse phase to minimize noise, vibration, and harshness effects due to apulse and glide type of cruise control.

The above described examples are provided to demonstrate differences ina pulse and glide type of cruise control. Additional variations arepossible. Furthermore, throughout a course of cruise control operationan engine controller may vary duty cycle, first and second thresholdvalues, aggressiveness of fueling, and/or the shape or slope of a pulsephase to further maximize fuel efficiency or minimize noise, vibrationand harshness.

The present disclosure describes systems and methods for controlling thespeed of a vehicle comprising: during a pulse phase of cruise control,applying engine torque to raise speed, the amount and duration of whichbeing responsive to engine speed; and during a glide phase of cruisecontrol, discontinuing engine combustion. In this way cruise control maymaintain a mean speed equivalent to a desired, threshold speed whilereducing fuel consumption, and NVH effects felt by the end user comparedto traditional cruise control methods.

Whilst specific embodiments of the present disclosure have beendescribed above, it will be appreciated that departures from thedescribed embodiments may still fall within the scope of the presentdisclosure.

It will be appreciated that the configurations and methods disclosedherein are exemplary in nature, and that these specific embodiments arenot to be considered in a limiting sense, because numerous variationsare possible. For example, the above technology can be applied to V-6,I-4, I-6, V-12, opposed 4, and other engine types. The subject matter ofthe present disclosure includes all novel and non-obvious combinationsand sub-combinations of the various systems and configurations, andother features, functions, and/or properties disclosed herein.

The following claims particularly point out certain combinations andsub-combinations regarded as novel and non-obvious. These claims mayrefer to “an” element or “a first” element or the equivalent thereof.Such claims should be understood to include incorporation of one or moresuch elements, neither requiring nor excluding two or more suchelements. Other combinations and sub-combinations of the disclosedfeatures, functions, elements, and/or properties may be claimed throughamendment of the present claims or through presentation of new claims inthis or a related application. Such claims, whether broader, narrower,equal, or different in scope to the original claims, also are regardedas included within the subject matter of the present disclosure.

The invention claimed is:
 1. A method of automatically controlling aspeed of a vehicle, comprising: receiving an input from a driver toenter a cruise control mode; determining a threshold speed; increasingthe vehicle speed to a speed which is a first predetermined value abovethe threshold speed; decreasing the vehicle speed to a speed which is asecond predetermined value below the threshold speed; and repeating thesteps of increasing and decreasing the vehicle speed until an input isreceived to exit the cruise control mode; and further comprisingdetecting a vehicle in front, determining a distance to the vehicle infront, maintaining the vehicle in front within a distance range to thevehicle in front and calculating the first predetermined value and thesecond predetermined value dependent on the distance to the vehicle infront.
 2. The method as claimed in claim 1, wherein the threshold speedcorresponds to a current speed of the vehicle and the threshold speed isadjustable by the driver during the cruise control mode.
 3. The methodas claimed in claim 1, wherein increasing the vehicle speed comprisesincreasing an amount of fuel supplied to an engine to cause vehicleacceleration.
 4. The method as claimed in claim 1, wherein decreasingthe vehicle speed comprises decreasing an amount of fuel supplied to theengine to cause vehicle deceleration.
 5. The method as claimed in claim1, wherein decreasing the vehicle speed comprises disengaging atransmission clutch of the vehicle.
 6. The method as claimed in claim 1,wherein at least one of the first and the second predetermined values isselected to produce an optimal brake specific fuel consumption valuefrom the engine.
 7. The method as claimed in claim 1, wherein at leastone of the first and second predetermined values is a predeterminedpercentage above the threshold speed.
 8. The method as claimed in claim1, further comprising reducing audio, visual or tactile phenomenaassociated with a repeated change in the vehicle speed.
 9. The method asclaimed in claim 8, further comprising reducing the audio, visual ortactile phenomena associated with the repeated change in the vehiclespeed by reducing a sound produced by the engine.
 10. The method asclaimed in claim 8, further comprising reducing the audio, visual ortactile phenomena associated with the repeated change in the vehiclespeed by varying a duty cycle of the engine.
 11. The method as claimedin claims 8, further comprising reducing the audio, visual or tactilephenomena associated with the repeated change in the vehicle speed bychanging the vehicle speed at a rate which is less perceptible to thedriver.
 12. A method of automatically controlling a speed of a vehicle,comprising: receiving an input from a driver to enter a cruise controlmode; determining a threshold speed; increasing the vehicle speed to aspeed which is a first predetermined value above the threshold speed;decreasing the vehicle speed to a speed which is a second predeterminedvalue below the threshold speed; repeating the steps of increasing anddecreasing the vehicle speed until an input is received to exit thecruise control mode; and reducing audio, visual or tactile phenomenaassociated with the repeated change in the vehicle speed by using afilter to alter a tachometer display.
 13. The method as claimed in claim12, further comprising detecting a vehicle in front, determining adistance to the vehicle in front, maintaining the vehicle within adistance range to the vehicle in front and calculating the firstpredetermined value and the second predetermined value dependent on thedistance to the vehicle in front.
 14. A method, comprising: reducingnoise, vibration and harshness during pulse and glide cruise control by,filtering a tachometer output; adjusting a rate of acceleration during apulse phase; varying a duty cycle of the pulse phase; and adjusting adifference between a high speed and a low speed.
 15. The method asclaimed in claim 14, wherein varying the duty cycle of the pulse phasefurther comprises increasing a duration of fueling.
 16. The method asclaimed in claim 14, wherein adjusting a difference between a high speedand a low speed further comprises reducing the difference between thehigh speed and the low speed.